It is a non-linear map which have many paths to take and reach the end. The point is, that you play a map one time and you are happy. Then you have a little break in Portal, because there aren't any new released maps for some time. But the answer is here: play the Deja-Vu again, but choose a different path with different puzzles. You can choose freely the way that is going to lead you to the end. Thats it!
This is not the full trailer of the mod, it's just a trailer i made so that you guys, who are waiting for this mod, know that it isn't dead. We're still working hard on it. When the map is around 80% done, the real official trailer will be out.